package array;

import java.util.Arrays;

public class SortThreeColor
{

  /*
   * Given an array with n objects colored red, white or blue, sort them so that
   * objects of the same color are adjacent, with the colors in the order red,
   * white and blue.
   * Here, we will use the integers 0, 1, and 2 to represent the color red,
   * white
   * , and blue respectively.
   * Note:
   * You are not suppose to use the library's sort function for this problem.
   * Follow up:
   * A rather straight forward solution is a two-pass algorithm using counting
   * sort.
   * First, iterate the array counting number of 0's, 1's, and 2's, then
   * overwrite array with total number of 0's, then 1's and followed by 2's.
   * Could you come up with an one-pass algorithm using only constant space?
   */

  // worked!!!!
  public void sortColors(int[] A)
  {
    int n = A.length;
    if (n < 2) return;
    int start = 0;
    int end = n - 1;

    int i = 0;
    while (start <= n - 1 && A[start] == 0)
      start++;
    while (end >= 0 && A[end] == 2)
      end--;

    while (i <= end && start < end) {
      if (i < start) i = start;
      if (A[i] == 0) {
        swap(A, i, start);
        start++;
      }
      else if (A[i] == 2) {
        swap(A, i, end);
        end--;
      }
      else {
        i++;
      }
      while (start <= n - 1 && A[start] == 0)
        start++;
      while (end >= 0 && A[end] == 2)
        end--;
    }
  }

  public void swap(int[] A, int i, int j)
  {
    int temp = A[i];
    A[i] = A[j];
    A[j] = temp;
  }

  // work under C++
  public void sort(int[] A)
  {
    int n = A.length;
    if (n <= 1) return;
    int zeroptr = 0;
    int twoptr = n - 1;
    int i = 0;
    while (A[zeroptr] == 0)
      zeroptr++;
    while (A[twoptr] == 2)
      twoptr--;
    while (zeroptr <= twoptr && i <= twoptr) {
      if (i < zeroptr) i = zeroptr;
      switch (A[i]) {
      case 0:
        swap(A, zeroptr, i);
        break;
      case 1:
        i++;
        break;
      case 2:
        swap(A, twoptr, i);
        break;
      default:
        break;
      }
      while (A[zeroptr] == 0)
        zeroptr++;
      while (A[twoptr] == 2)
        twoptr--;
    }
  }

  // correct
  public void sort1(int[] A)
  {
    int[] count = new int[3];
    for (int i = 0 ; i < 3 ; i++) {
      count[i] = 0;

    }

    for (int i = 0 ; i < A.length ; i++) {
      count[A[i]]++;
    }
    int start = 0;
    for (int i = 0 ; i < 3 ; i++) {
      for (int j = start ; j < start + count[i] ; j++) {
        A[j] = i;
      }
      start += count[i];
    }
    System.out.println(Arrays.toString(A));
  }

  /**
   * @param args
   */
  public static void main(String[] args)
  {
    // TODO Auto-generated method stub
    int[] A = new int[] { 0 };
    SortThreeColor s = new SortThreeColor();
    s.sortColors(A);
    System.out.println(Arrays.toString(A));
  }

}
